Theoretical study of the reaction of atomic hydrogen with acetonitrile

The reaction of atomic hydrogen with acetonitrile has been studied using th e B3LYP and Gaussian-3 (C3) methods. The geometries and vibrational frequen cies of various stationary points on the potential energy surface were calc ulated at the B3LYP level with the 6-311G(d,p) and 6-311++G(2d,2p) basis se ts. The energetics were refined at the G3 level. The G3 barrier height has been calibrated using a test set including 39 well-established reactions. I t is believed that the present potential energy surface is reliable within chemical accuracy. The title reaction starts in four manners, namely direct hydrogen abstraction, C-addition, N-addition, and substitution. The corres ponding barrier heights (including ZPE corrections) are 12.0, 7.6, 9.6, and 44.7 kcal/mol, respectively. The kinetics of the reaction were studied usi ng the TST and multichannel RRKM methodologies over the temperature range 3 00 similar to 3000 K, and were compared with the earlier experimental data. At lower temperatures, the C-addition step is the most feasible channel, a nd the major products are CH3 and HCN at lower pressures. At higher tempera tures, the direct hydrogen abstraction path leading to H-2 and CH2CN is app arently dominant.